The present invention relates generally to the field of electronic system testing. More particularly, the present invention relates to devices and methods for testing signal paths in electronic systems.
Electronic systems are prevalent in the modern world, and reliable operation of these devices is highly desirable. An important component of electronic systems are the signal paths within those systems. Signal paths can be provided by wires, cables, circuit board traces, wireless links, and the like. Signal paths may be relatively short, for example, a connection between two components in a circuit, or relatively long, for example miles of wiring used in a telephone system. Unfortunately, the reliability of an electronic system can be adversely affected by an anomaly in one of its signal paths.
For example, aircraft provide a particularly poignant example: failures in the wiring of an aircraft can cause catastrophic results. Aircraft wiring can prove difficult to test, however, at it is often inaccessible. Furthermore, intermittent failures can occur in flight that are difficult to reproduce under the differing vibration, altitude, temperature, and humidity conditions that occur on the ground. Productive time is lost when aircraft must be grounded; yet, technicians may be unable to find the cause of a failure.
Testing of signal paths in electronic systems can be difficult, however, as wires are often inaccessible, hidden behind panels, wrapped in protective jackets, or otherwise difficult to access. Removal of wires for testing or inspection can cause damage, and even if the wires are functioning properly upon inspection, reinsertion of the wires into the system can cause damage.
Testing of signal paths also typically requires shutting the system down while the testing is being performed. For example, testing often requires applying a small voltage to the signal path and measuring the resulting current to test for open or short circuits. If an operational signal is present, the measurement may be erroneous. More sophisticated techniques involve injecting other types of test signals into the signal path, and can be disrupted if an operational signal is present. Furthermore, injecting a test signal into the signal path while the system is operational can result in disruption to the system. Shutting down the system for testing can be both inconvenient and expensive if revenues are lost while the system is shut down. Furthermore, some types of intermittent faults may be very difficult to detect in this manner.